Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn钛合金的动态力学性能及失效研究

Research on dynamic mechanical properties and failure of Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn alloy

摘要:

本文针对近β型Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn新型钛合金,研究了轧制及热处理两种状态下材料的动态力学性能及其失效行为。经880℃多道次轧制,获得由β相基体及“等轴+条状”非均匀分布的α相组成的双态组织；经895℃保温0.5h炉冷热处理后,其组织则由β相及完全等轴化的α相构成。3100s_^-1~3800s_^-1不同应变率条件下的动态压缩试验结果表明,轧制态钛合金较热处理态钛合金的动态压缩强度高出约200MPa~400MPa,最高可达2133MPa,但其临界断裂应变则明显较低,最高仅10.8%；热处理后,虽然动态压缩强度有所下降,但临界断裂应变最高可达23.6%,表现出良好的强塑性匹配特性。进一步研究发现,轧制态钛合金高的位错密度及非均匀的组织分布特征,导致其在动态压缩过程中出现分叉的绝热剪切带,断口呈现出平滑区及韧窝区两种特征,表明其断裂机制为脆性断裂+韧性断裂；而热处理态钛合金断口则以韧窝区为主,表明其断裂机制为韧性断裂。相关研究为该新型合金的工程化制备及应用提供了理论及技术支撑。

Abstract:

In this paper, the dynamic mechanical properties and failure behavior of rolled and heat treated Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn alloys were studied. After multi-pass rolled at 880℃, a duplex microstructure consisting of β matrix and non-uniformly distributed _^-1~3800s_^-1 show that the dynamic compression strength of rolled titanium alloys is about 200MPa~400MPa higher than that of heat treated titanium alloys, with a maximum value of 2133MPa, but the critical fracture strain is obviously lower, with a maximum value of only 10.8%. Although the dynamic compression strength of titanium alloys decreases after heat treated, the critical fracture strain can reach 23.6%, showing better matching feature of strength and plasticity. Further study found that the characteristic of high dislocation density and inhomogeneous structure distribution of rolled titanium alloys result in bifurcated adiabatic shear bands during dynamic compression tests. The fracture surfaces of rolled titanium alloys show two characteristics: smooth zone and dimple zone, indicating that the fracture mechanism is brittle fracture + ductile fracture, while that of heat treated titanium alloys is mainly dimple zone, indicating that the fracture mechanism is ductile fracture. The research provides theoretical and technical support for the engineering preparation and application of the new alloy.